The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art.
Hybrid powertrain architectures include torque-generative devices, including internal combustion engines and electric machines, which transmit torque through a transmission device to a vehicle driveline. Exemplary electro-mechanical transmissions are selectively operative in fixed gear modes and continuously variable modes through application of torque transfer devices. A fixed gear mode occurs when rotational speed of the transmission output member is a fixed ratio of rotational speed of the input member from the engine, typically due to application of one or more torque transfer devices. A continuously variable mode occurs when rotational speed of the transmission output member is variable based upon operating speeds of one or more electrical machines. The electrical machines can be connected to the output shaft via application of a torque transfer device, or by direct connection. Application of a torque transfer device including a hydraulic clutch is typically effected through a hydraulic circuit, including electrically-actuated hydraulic flow management valves, pressure control solenoids, and pressure monitoring devices controlled by a control module. Application of a torque transfer device including a one-way clutch is typically effected when a driving member is rotating in a first direction in which the one-way clutch has capacity. However, when the driving member is rotating in an opposite or second direction, the one-way clutch will release or decouple the driving member from the driven member or ground.
It is known that torque transfer device slip speeds are determined from motor, engine and output speed signals. As a result of transmission delays, sensor error, and the transient nature of the torque generating speed sources, slip speeds on applied torque transfer devices are often noisy
It is further known to detect failures in torque transfer devices when an existing torque transfer device slip speed exceeds a threshold for a predetermined period of time. This failure diagnostic necessitates including the slip performance between large magnitudes of slip speed for a short amount of time and small magnitudes of slip speed for long amounts of time. Typically, the slip speed failure threshold must be set above the typical noise band in the signal to avoid false failures of the diagnostic, resulting in delayed detection of real failures.